1. Field of the Invention
The present invention relates to an internal combustion engine control apparatus that identifies cylinders of an internal combustion engine based on a crank angle position signal from a sensor mounted on a crankshaft and a cylinder identification signal from a sensor mounted on a camshaft, and more particularly, it relates to such an internal combustion engine control apparatus that is provided with an abnormality detection means and a fail safe function for abnormal situations.
2. Description of the Related Art
In general, in an apparatus for controlling an internal combustion engine such as an automotive engine or the like, it is necessary to optimally control the injection of fuel, the ignition timing, etc., in accordance with the operating conditions of the engine. In order to control the internal combustion engine, it is necessary to acquire a reference crank angle position signal representative of a reference crank angle position of each cylinder and a cylinder identification signal for identifying a specific cylinder.
Accordingly, for instance, a signal generation means including electromagnetic sensors is installed on rotation shafts such as a crankshaft, a camshaft, etc., of the internal combustion engine, and based on the reference crank angle position signal and the cylinder identification signal generated from the signal generation means, the reference crank angle position of each cylinder is recognized and each cylinder is identified, so that the injection of fuel and the ignition timing can be controlled with high accuracy.
That is, the conventional internal combustion engine control apparatus is provided with a crank angle sensor mounted on the crankshaft and a cam angle sensor mounted on the camshaft that makes one revolution every two revolutions of the crankshaft.
The crank angle sensor outputs a pulse-shaped crank angle position signal at prescribed crank angle intervals (for instance, at every 10xc2x0 crank angle (CA)) corresponding to projections on the outer periphery of a ring gear mounted on the crankshaft, and the cam angle sensor outputs a cylinder identification signal corresponding to each cylinder.
In addition, there has been proposed such an apparatus in which an untoothed or lost tooth portion (for instance, corresponding to 30xc2x0 CA) is provided in a part of a crank angle position signal, and which is capable of performing accurate cylinder identification by detecting a reference crank angle position corresponding to this untoothed portion and using it in combination with a cylinder identification signal.
A reference crank angle position detection means related to a crank angle sensor detects the reference crank angle position in real time, and a cylinder identification signal generation means related to a cam angle sensor generates a cylinder identification signal in real time.
Moreover, a cylinder identification means related to the reference crank angle position detection means and the cylinder identification signal generation means performs cylinder identification in response to the reference crank angle position signal and the cylinder identification signal in real time.
However, if there would take place abnormality in either of the crank angle position signal or the cylinder identification signal, the detection of the crank angle position and the identification of each cylinder could not be carried out correctly.
Thus, when abnormality occurs in either of the crank angle position signal or the cylinder identification signal, it is necessary to detect the state of abnormality occurrence at once and perform fail safe processing so as to avoid mis-control on the internal combustion engine.
There has been known an internal combustion engine control apparatus with such a fail safe processing function which is described in Japanese Patent Application Laid-Open No. Hei 7-197843 for instance.
In the conventional apparatus as set forth in this document, even when the superposition of noise or signal dropout are generated in the crank angle position signal, the reference crank angle position is redetermined based on the untoothed or lost tooth portion, so that the cylinder numbers are re-set according to the number of pulses of the crank angle position signal between the lost teeth upon the redetermination of the reference crank angle position, thus preventing the identified cylinder number from being shifted and hence made incorrect.
Moreover, in another conventional apparatus such as, for example, the one described in Japanese Patent Application Laid-Open No. Hei 9-170484, the number of pulses of the crank angle position signal between successive input timings of the cylinder identification signal is counted so that the number of pulses thus counted is compared with a prescribed determination value thereby to make a determination as to whether there is abnormality in the cylinder identification signal.
However, it is thought that with respect to the crank angle position signal and the cylinder identification signal, noise superposition, signal dropouts or the like may take place not only sporadically but also successively or intermittently.
For instance, according to the above-mentioned Japanese Patent Application Laid-Open No. Hei 7-197843, when there sporadically takes place noise superposition or signal dropout in the crank angle position signal, it is possible to prevent a shift of the cylinder numbers.
However, according to the method described in the Japanese Patent Application Laid-Open No. Hei 7-197843, when there occurs noise superposition or signal dropout successively or intermittently by some causes, the injection of fuel and the ignition timing might be controlled on incorrect cylinders (or at incorrect timing), and if the ignition control would be carried out on incorrect cylinders (or at incorrect timing), it could cause backfiring, engine damage, etc.
Further, in the method described in the other Japanese Patent Application Laid-Open No. Hei 9-170484, since it is presupposed that the crank angle position signal be normal, it is necessary to determine in which of the crank angle position signal and the cylinder identification signal there has taken place abnormality. Besides, there has been no description at all about fail safe processing needed upon abnormality determination.
As described above, the conventional internal combustion engine control apparatuses have a problem that they cannot detect abnormality (noise superposition, signal dropout, etc.) that might occur in the crank angle position signal and the cylinder identification signal with high reliability, and that no fail safe function can be ensured upon occurrence of abnormally.
Specifically, the conventional apparatus according to Japanese Patent Application Laid-Open No. Hei 7-197843 involves a problem that when noise superposition or signal dropout in the crank angle position signal takes place successively or intermittently, the injection of fuel and the ignition timing might be mis-controlled, which would cause backfiring or engine damage especially when such mis-control is performed with respect to ignition control.
On the other hand, the conventional apparatus according to Japanese Patent Application Laid-Open No. Hei 9-170484 has a problem that it is necessary to determine in which of the crank angle position signal and the cylinder identification signal there has taken place abnormality, and that no consideration is given to the fail safe processing which is needed when a determination of the presence of abnormality is made, and hence it is impossible to ensure a fail safe function upon occurrence of abnormally.
The present invention is intended to solve the problems as referred to above, and has for its object to provide an internal combustion engine control apparatus which is capable of detecting a state of abnormality (noise superposition, signal dropout, etc.) that might be generated in a crank angle position signal or a cylinder identification signal with high reliability, thereby making it possible to ensure a fail safe function upon occurrence of abnormally.
Another object of the present invention is to provide an internal combustion engine control apparatus which is capable of continuing the operation of an internal combustion engine while preventing the crank angle position and cylinder identification from being misjudged when a state of abnormality in the crank angle position signal or in the cylinder identification signal has taken place sporadically.
A further object of the present invention is to provide an internal combustion engine control apparatus which is capable of promptly stopping the engine when a state of abnormality has taken place successively (i.e., when backfiring or engine damage might be caused if the operation of the engine is continued).
A still further object of the present invention is to provide an internal combustion engine control apparatus which is equipped with an abnormality detection means and a fail safe function by which when a state of abnormality has taken place intermittently, a minimum limp home capability can be ensured by continuing fuel injection control and ignition timing control on the cylinder(s) or period(s) of time for which the cylinder identification is correctly carried out.
Bearing the above objects in mind, the present invention reside in an internal combustion engine control apparatus for identifying a plurality of cylinders of an internal combustion engine to control the injection of fuel and ignition timing with respect to each of the cylinders. The apparatus includes: a crank angle position signal generator mounted on a crankshaft of the internal combustion engine for generating a crank angle position signal in the form of a train of a plurality of pulses corresponding to a plurality of rotational angle positions of the crankshaft; a cylinder identification signal generator mounted on a camshaft that rotates at a rate of one revolution per two revolutions of the crankshaft for generating a cylinder identification signal in the form of a train of a plurality of pulses corresponding to a plurality of rotational angle positions of the camshaft, and to the cylinders. A reference crank angle position detector detects reference crank angle positions included in the crank angle position signal. A cylinder identification part identifies each of the cylinders based on the cylinder identification signal. A cylinder control part generates a fuel injection signal and an ignition signal with respect to each of the cylinders based on the result of cylinder identification performed by the cylinder identification part and the crank angle position of the crank angle position signal. An abnormality determination part determines the presence or absence of abnormality at least in the crank angle position signal. The cylinder identification part includes a cylinder identification resetting part for resetting the current cylinder identification content of the cylinder identification part when it is determined that the crank angle position signal is abnormal. The cylinder identification resetting part includes: a fuel injection and ignition signal stopping part for stopping the fuel injection signal and the ignition signal; and a cylinder identification information clearing part for clearing previous cylinder identification information earlier than the last crank angle position signal at the time of the determination of abnormality.
According to the present invention, it is possible to detect an abnormal state (noise superposition, signal dropouts, etc.) that might be generated in the crank angle position signal, thereby making it possible to ensure a fail safe function upon occurrence of abnormality in the crank angle position signal.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.